1. Field of the Invention
The present invention relates to wireless communication, and more particularly, to a method and apparatus for controlling transmit power in a wireless communication system.
2. Discussion of the Related Art
Long term evolution (LTE) based on 3rd generation partnership project (3GPP) technical specification (TS) release 8 is a promising next-generation mobile communication standard.
As disclosed in 3GPP TS 36.211 V8.5.0 (2008-12) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)”, a physical channel of the LTE can be classified into a data channel, i.e., a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH), and a control channel, i.e., a physical downlink control channel (PDCCH), a physical control format indicator channel (PCFICH), a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH), and a physical uplink Control channel (PUCCH).
A PDCCH (i.e., a downlink control channel) carries a downlink grant for receiving the PDSCH of a user equipment (UE) and an uplink grant for transmitting the PUSCH of a UE. A PUCCH (i.e., an uplink control channel) carries an uplink control signal (e.g., positive-acknowledgement (ACK))/negative-acknowledgement (NACK) signals for a HARQ), a channel quality indicator (CQI) indicating the condition of a downlink channel, an SR (Scheduling Request) for requesting the allocation of radio resources for uplink transmission, and so on.
To guarantee a higher data rate, a technique using a multi-antenna has been introduced.
Through transmit diversity and spatial multiplexing, multiple antenna transmission can achieve higher link performance compared to single antenna transmission.
The conventional 3GP LTE does not support multiple antenna transmission in uplink. However, as a next generation communication system employs the multiple antenna uplink, uplink transmit power is needed to consider multiple antenna transmission.